Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Regulator failure? Help needed!

[Harv748]

During the last session of my TD yesterday, the SP started to cough and splutter a bit...and coincided with the rev guage dropping down and showing eratic behaviour.

Also...it seemed a little sluggish off the starter button, as if the battery was losing its charge.

As it was the last session, and I have since been unable to take a further look at the bike...I have no more information to share, but does this ring any bells and is it as I think related to the regulator.

The bike is a 1995 SP, but does have the newer version regulator (with the big metal back plate and heat fins on the reg itself).

So before I go out there and try and get to the bottom of things...where do I start.

Please keep in mind that my electrical knowledge is very limited...although I do own a small digital multi-meter!!

An idiots guide/step by step would be good!

[nelly]

Apart from regulator failure, the usual suspects are the two yellow wires feeding the charge from the alternator to the reg.
If you take th ebattery trya off, there's two connectors to the reg. One is a 4 way jobbie, the other a two way. It's this one that connects the yellow wires.
Check the wires and connector. They've probably melted.
Cut the connector out, cut the wires back to good and fit bullet connectors. Wrap them in tape to keep the muck out.
You can solder them but this makes servicing a pain as you can't remove the tray out of the way

[Derek]

As Nelly says - check the connector with the yellow wires.
Further, if you have access to a digital multimeter connect it across the two yellow wires with it set to read AC volts. With the engine running you should get a reading of approx 15V/1000rpm. i.e. 30v at 2000rpm or 60v at 4,000rpm. If you get something like this then the stator is OK.
Then connect it across the battery with it set to DC volts. With the battery in a good state of charge it should read about 12.5V or so. Start the bike and watch the meter. It should rise to at least 13.8V at 2,000rpm and not exceed 14.6 volts at any revs. If no rise in volts at the battery or it rises too much then the regulator is duff.

[Harv748]

OK...all sounds easy enough!

Gonna give it a go tonight...

[moto748]

The replacement of the connectors nelly mentions is really worthwhile; do do it if it hasn't already been done. The stock ones really aren't up to the job. I used the "block connector" type with the little screws (like the connections in a 3-pin domestic plug). That's another alternative to crimped/soldered bullet connectors.

[Harv748]

OK...just had a look and indeed the connecting block for the yellow wires is looking a bit sad (burnt)...so I assume this means the reg is knackered then?

I'm going to strip them back and reconnect as suggested.

Do I still need to check that the reg is gone or do I assume its past its best and invest in a new one? And if so...which, as I have read a few things about Eletrix ones or summut?

[748mart]

The regulator should be OK, as suggested strip back reconnect the yellow wires & check battery voltage is between 13.5v - 14.5v at 2k rpm

[Edited on 8-6-2005 by 748mart]

[Harv748]

So if the regulator is/could be OK, what was the actual cause of the problem? The wiring, bad connector(s) block???

[rockhopper]

damp in the connector causing a high resistance and over heating. Mine did the same thing but i didnt make it home.

[Shazaam!]

The most common reason for an erratic charging voltage is that the stator lead wire insulation is heat damaged allowing them to short together, especially after the engine heat further reduces the electrical insulating capability of the wires. Ducati has supplied seriously under-sized wires - given that they have to carry 30-plus amps continuously. Replacing the wires between the engine casing and the regulator with a heavier gauge cures the problem - if done soon enough. If not, the voltage surges from the wires being shorted together end up damaging the solid state components in the regulator/rectifier and you’ll soon end up having to replace it as well.

So first the wires from the stator to the regulator need to be replaced. At first glance it may appear that the high current being carried by the wire had just overheated a few inches of insulation next to the high-resistance bullet connectors. But when you remove the common sheath that the wires run in back to the left engine cover, you likely find that overheating (from the current, not the engine) has softened the insulation to a degree where you can damage it with your fingernail. A multimeter will say it's continuity is OK but at the higher AC output levels at higher rpms the insulation can’t prevent the wires from shorting together. Remember, the wires are held in physical contact along the entire sheath length.

You don’t really need to remove the engine cover. Inside the engine the wires don't touch each other. The approach that I took was to replace the damaged wiring (with a larger gauge to reduce electrical heating) up to where it exits the side cover. I pushed a piece of shrink wrap tubing over each of the wires and into where they pass through the seal in the cover and left the internal portion of wiring alone since they are separated inside the engine. Again, the main problem is where they touch each other along their length where they run in a common sheath.

I also took the oportunity to relocate the regulator itself to the licence plate holder to get it away from the engine and exhaust heat.

You can read the full explanation here:

http://ducatisportingclub.com/contro...d.php?tid=2042